Molecular Characterization And Biological Function Of Fusarium Oxysporum Fructus Gβ-like Protein CpcB (Cross Pathway Control B)

Aspergillus fumigatus is an airborne and environmentally ubiquitous opportunistic pathogen, which can cause severe invasive infections in immunocompromised hosts. A. fumigatus conidia, are really contagious propagules, so the understanding of the regulatory mechanisms of asexual sporulation is vital for effective control of aspergillosis. Studies have shown that G protein signaling pathway plays an important role in regulating mycelial morphology, growth and spore production in A. fumigatus Canonical heterotrimeric G protein complexes are composed of Gα, Gβ, and Gy subunits. Studies have reported that a Gβ-like protein CpcB in A. fumigatus, which is similar to signal transduction protein, plays important roles in regulating hyphal growth and development, and is also an important protein related to virulence. It has not been reported whether the virulence-associated protein CpcB in A. fumigatus, which is a member of amino acid metabolism pathway (Cross pathway control), has a role in the metabolism of amino acids. CpcB possess conserved motifs and amino acids. However, as a conserved Gβ-like protein, the molecular characteristics of CpcB have not been identified yet. Therefore, it is urgently necessary to evaluate the molecular characteristics of CpcB to understand its further function.Gβ-like CpcB protein containing seven WD repeats belongs to a WD40 repeat protein family, which possess a common β-propeller structure with conserved G-H and W-D residues in WD repeat. In this study, we demonstrated that WD repeats are responsible for normal hyphal growth and conidiation through truncation experiment. Moreover, we identified that three G-H residues in WD repeat 1,2,3 and the W-D residue in WD repeat 2 are required not only in controlling normal hyphal growth and conidiation but also in affecting the antifungal drug susceptibility. Using analyses of flow cytometry and HPLC, we found the possible reasons of enhanced drugs resistance are the reduced intracellular drug accumulation and altered ergosterol component. In addition, the first G-H residue mutant causes the significant attenuated virulence consistent with the full-length deletion of cpcB. Therefore,our finding provides that Gβ-like protein CpcB (Cross pathway control B) plays an important role in the regulation of drug susceptibility and virulence. It is a great significance in exploring the role of Gβ-like homologous proteins or other family members of Cross Pathway Control in virulence. Moreover, this is the first report about the importance of conserved G-H and W-D residues for a Gβ-like protein, which provides novel insights into the function of other conservative protein.